Regional stratigraphically discordant dolomite mapping based on a dolomitization mechanism on the Arabian carbonate shelf

Abstract

Dolomite mapping, as a first step of carbonate diagenetic modeling, is critical to understanding dolomitization mechanisms and predicting reservoir quality. Stratigraphically discordant dolomite bodies within the Upper Jurassic intervals have long been studied on the Arabian shelf. Our dolomitization mechanisms find that faults/fractures serve as migration conduits and determine dolomite distribution by controlling fluid flow. We establish an innovative approach based on the diagenetic mechanisms and comprehensive characterization of fracture systems at multiple scales to delineate dolomite in the study area. The complex fracture networks in the subsurface are categorized into macroscale, mesoscale, and microscale fractures. Macroscale fractures, i.e., faults, are much greater than the seismic wavelength and are easily observed in seismic sections due to their obvious seismic discontinuities. Mesoscale fractures are slightly greater than or equal to the seismic wavelength and are recognized using seismic attributes. Microscale fractures are significantly smaller than the seismic wavelength and are observed mainly on core samples and thin sections. The dolomite mapping workflow includes three steps: (1) calibrate the seismic response of multiscale fractures with borehole image logs and core interpretations, (2) implement multiscale fracture characterization using multiple seismic attributes, and (3) interpret dolomite bodies based on fracture characterization and log identification. The mapping results show that massive dolomite bodies are heterogeneously developed and distributed mainly in the northeastern part of the study area, with a southward decrease in dolomite content. The application demonstrates that multiscale fracture systems play critical roles in massive dolomitization, and multiscale fracture prediction provides an innovative solution to delineate complex dolomitization systems and the combination of reservoir and seal in diagenetic traps.